Dialysis of a patient having renal failure can involve peritoneal dialysis or hemodialysis. In hemodialysis, blood is cyclically withdrawn from the patient, circulated through a filtration system, and returned to the patient. This requires access to the patient's circulatory system, which can be accomplished with a catheter or shunt. A dialysis shunt connects a portion of the arterial system to the venous system such that blood flows through the shunt and bypasses a section of the patient's body (e.g., a hand in the case of dialysis via the forearm) that the artery ordinarily supplies with blood. The shunt can be a fistula or graft. A fistula is a direct connection of an artery and vein, and a graft connects an artery and vein. A surgically created shunt requires time to mature before using it for dialysis. Often, the maturation time necessitates placement of a temporary dialysis method.
Decreased supply of blood to an extremity, e.g., a foot or hand, can lead to ischemia, which can create a condition such as a cold limb or, in more severe cases, tissue damage due to deprivation of oxygen, glucose, and similar compounds required for cellular metabolism. Moreover, stagnation of blood in the shunt or blood vessel can lead to thrombosis, failure of the shunt, complications including embolism, and additional surgical or interventional procedures with their inherent risks and costs.
Further, each hemodialysis session usually lasts for three to four hours and is usually performed three times per week. During the time that dialysis is not performed, a shunt has blood flowing through it. Consequently, blood may flow through the shunt greater than 90% of the time without benefit and possibly causing harm. Constant flow of blood through the shunt can cause the formation of a blockage and failure of the shunt or dialysis system. A shunt can fail due to developing such a blockage that causes blood stagnation in the shunt, in the inflow arterial system, or in the outflow venous system, with subsequent clot formation. Clotting of the shunt requires a surgical or radiological procedure, time, and expense to restore blood flow.
Hence, new materials and methods for implants should be well received in the art.